Iconography
The Citipati are two skeletons, one of a man and the other of a woman, represented with arms and legs interlaced, dancing the Tsam dance. They are considered to be masters of the cemetery. The Citipati are one of the seventy-five forms of Mahakala and are visible reminders of the impermanence of everything worldly. Their mouths are parted in a large grin, showing all their teeth. Each wears a long scarf. According to a Northern Buddhist legend, the Citipati were, in a former existence, two ascetics who were once lost in such deep meditation that they did not notice that a thief had cut off their heads and thrown them in the dust. Since that time they have been ferocious enemies of thieves, having vowed eternal vengeance. This legend is somewhat similar to that of Yama. In the cemetery, the Citipati are supposed to perform a skeleton ritual dance during which they blow the Tibetan long horns. In most monasteries the dance, symbolic of the cycle of life and death, is performed in the monastery cemetery once in summer and once in winter by monks wearing masks.

Symbolism of Impermanence: The skull is a potent symbol of impermanence (anicca) and the transient nature of life. It serves as a reminder of mortality and the inevitability of death, encouraging practitioners to contemplate the impermanent nature of all phenomena.

Symbol of Wisdom (Kapala): In certain Buddhist traditions, particularly in Vajrayana (Tibetan Buddhism), the skull can be specifically referred to as a "kapala," which translates to "skull cup." A kapala is a ritual implement made from a real human skull used in certain tantric practices. It symbolizes the transformation of negative emotions into wisdom and the transcendence of ego-based attachments.
Use in Tantric Rituals: Within Vajrayana Buddhism, the kapala plays a ritualistic role in ceremonies known as Chod (or "cutting through ego"), where practitioners visualize offering their own body as a feast to spiritual beings. This practice symbolizes the practitioner's fearless engagement with impermanence and the ultimate reality of emptiness.

Artistic Symbolism: In Buddhist art, skulls can be depicted as adornments or decorative elements on wrathful deities or protectors, symbolizing their transcendence over death and ego. Skulls may also be featured in thangka paintings, sculptures, and ritual objects as a potent symbol of transformation and spiritual realization.

Cultural Context: The significance of the skull in Buddhist culture reflects broader themes of Buddhist philosophy, including the Four Noble Truths and the practice of mindfulness of death. Meditating on the image of a skull is a contemplative practice aimed at deepening insight into the nature of existence.

Ethical Considerations: It's important to note that in Buddhist contexts, the use of actual human remains (such as kapalas) in rituals is subject to ethical guidelines and cultural sensitivities. Many modern practitioners use symbolic representations of skulls or other ritual objects to engage with the teachings of impermanence and wisdom.

In summary, the Buddhist skull symbolizes profound spiritual themes related to impermanence, wisdom, and transformation within Buddhist philosophy and practice. Its symbolism invites practitioners to contemplate the nature of existence and the path towards awakening, emphasizing the impermanent and interconnected nature of all phenomena.